In a shift register unit in related art, a pull down gate driving signal is controlled by a pull-down node in an output off maintenance phase. However, a time for pulling down the gate driving signal in the output off maintenance phase is 50%, while in another time when the gate driving signal is not pulled down, it is possible that the gate driving signal cannot be maintained at a low level due to leakage of electricity of the pull-up transistor. Therefore, reduction of noise cannot be performed well on the gate driving signal.